What coils/spring rates for midsize E/UHP wheels (weekend/hobby drive)?

[Tor]

First of all, thank to all that contribute here on the forums. Along with the many that videoblog, I think the many evenings of reading and watching has helped me, hopefully, get a better understanding about suspension, and hence to make a better decision about how to mod my car. I am looking for some specific advice about what coilovers to get for my situation:


1) Weekend drives on backroads (like those here): [ame="https://www.youtube.com/watch?v=PMPn9TOH304"]Fun with GT86! - YouTube[/ame]


2) Going to and from work, when the sun is shining and I feel like it (it's not my daily drive). I won't be stuck in traffic it's pretty much the same roads as above to get there. I.e. I would take it, if I want an enjoyable drive and need not a huge emphasis on comfort.

3) I would like to start taking it to the track occasionally. I live in Germany only a good hour drive from Nürburgring and Spa isn't that far away either as examples. I would also like to take part in drivers courses and maybe do some auto cross at some point.

4) It would be nice to retain some capability to use the car for longer tours, like 500 miles autobahn (few times a year at most and I drive it with in ear noise reduction headset already on such stretches already). Or going away for the weekend.


As such, I would like to retain a good deal of street-ability, starting with wheels that remain practical. I got a set of used OZ 18x8 inch Ultraleggera wheels with Pirelli Nero GTs (bought the set for the rims). From what I read so far the Nero GTs didn't get the best reviews. I didn't have a chance to drive them myself yet (winter). The tire I am most interested in is the Yokohama AD08R, I had my eyes on those for so long, that those will probably be mounted in a matter of time.

Adjustable LCA are also on order and a brake line/pad upgrade will be done at next service. In a more distant future I would like a HKS compressor upgrade as well.

So to the question:
What coilovers would work well for me?
I initially looked at KW V3 4/5 kg, then KW Clubsport 6/7 kg, and after a lot of reading decided on the Öhlins Road & Track MI20 6/6kgs only to find out it has been discontinued.

I thought it would be more suitable for my needs because 1) as it's 1-way might be easier for a beginner like me and 2) the dampers were probably higher quality and 3) it appealed to me that they were the same rate front and rear.

Öhlins now make the MP20 with 4/3 kg spring rates. Initially I though it might be too soft, and it was weird with the soft spring in the rear. But from reading the advice of @Moto-P (http://www.ft86club.com/forums/showthread.php?t=10643), I am wondering if it after all might not be such bad a choice?

Moto-P:
Soft + mid-height -20~30mm (or plenty of stroke built into coilver) + medium grip street tire = FUN, Fairly quick, easy to handle, and close to original setup.

It's soft + it only lowers the car 20~30mm (the damper is probably high quality, has good stroke) + the AD08R is a ____ grip (medium or high in this context?) street tire.

Would the Öhlins MP20 be a perfect fit? I also consider AST, as they are fairly close to me. Would you advice to go with something harder for a tire in the category of AD08R and with the intended use?

Thanks for reading!

[go_a_way1]

Do you have a budget??

[Tor]

Preferably <4000$ and given that I want to use the car something that is durable and doesn't require a lot of maintenance.

[go_a_way1]

Originally Posted by Tor

Preferably <4000$ and given that I want to use the car something that is durable and doesn't require a lot of maintenance.

Okay, I would look into something you can get rebuilt local, as you may want to rebuild them every few years to keep then in tip top shape.

I also agree with you trying to stick to a 1 way system but if you buy a 2 way from a reputable dealer they can help you set them up I am sure.

I think you can get Ohlins built with custom specs cant you? Don't quote me on that but if you can I would go that route or if you want something really really good and are willing to pay a little more go with these.
http://counterspacegarage.com/jrz-rs1-brz-frs.html
I think you will have to contact them before you order them as they set them up to your car and needs as they are built to order.

If you want to take a cheaper road contact Fortune Auto (go for the 510)they also hand build their coils to order to your specs. I would call them and talk with them just to get an idea of what you are looking for, they know their stuff.

[Tor]

I should have mentioned that it should preferably be something I can source in Europe. The JRZ looks nice and I would be willing to go slightly above 4k for something extra nice. But unfortunately they will end up in 6k$+ with shipping and taxes.

I was thinking about the AST 1-Way 5100 too.
http://www.ast-suspension.com/websho...a-gt-86-detail

It's $2000 without options. With custom springs, a piston option that sounds fancy (double digressive, whatever that means) and top mounts it's a very reasonable $2500 and they are 2 hours drive away.

Here I could really use some advice regarding spring rates. Surely AST will have an opinion too, but still it would be nice to get some outside advice.

[strat61caster]

Originally Posted by go_a_way1

Okay, I would look into something you can get rebuilt local, as you may want to rebuild them every few years to keep then in tip top shape.

Bilstein would probably be his local option, B16 fits the bill under budget and can be adapted to his specs and chosen springs via revalving from someone local, faraway, or the factory, but that would take a ~$2k setup up to ~$3k+ and require some guesswork and trust with vendors, not everyone wants to go that route. They are maybe a little too street oriented in off the shelf configuration with spring rates on par with the soft Ohlins but that will help daily drivability.

Edit: Spring rates for B16 and B14 (cheaper no damping adjustment)
Front: 2.5-4.5kg progressive
Rear: 3.0-7.0kg progressive

[Racecomp Engineering]

Bilstein B16 PSS10 would be a good choice if you're okay with progressive springs. I don't prefer progressive springs for the track, but they're fine for fast back road fun.

The new Ohlins are very soft and I don't know if they have enough travel. We liked the old version on our car with the 6k and then custom 7k rates, but even then we wanted more stroke.

KW V3 would be a good choice. A little bit soft, but lots of stroke. They are comfortable and easy to drive fast when set up correctly. With the Advans you might be better suited to the KW Clubsports though. We make a custom valved and sprung KW clubsport over here and are very happy with them (RCE Tarmac 2).

AST is fine choice. It sounds like you get them a bit cheaper than we do over here.

- Andrew

[tyler_win_photo]

Typically you'd want stiffer springs to accommodate stickier tires like the AD08R.

[Racecomp Engineering]

Originally Posted by tyler_win_photo

Typically you'd want stiffer springs to accommodate stickier tires like the AD08R.

Right on, and those tires with the super soft Ohlins would be a poor match in my opinion.

- Andrew

[Kayshart]

For track situations, what would happen with a sticky tyre like AD08R with springs which are not stiff enough? Would this mean the suspension will be hitting the bumpstops through the corners? Would this worsen the car's handling? Would stiffening the damping help?

But wouldn't it still be better than having stiffer springs but crappy tyres?

Just for reference, my setup is koni shocks with RCE yellow springs 4.5kg square.

Sent from my LG-H815 using Tapatalk

[Racecomp Engineering]

Originally Posted by Kayshart

For track situations, what would happen with a sticky tyre like AD08R with springs which are not stiff enough? Would this mean the suspension will be hitting the bumpstops through the corners? Would this worsen the car's handling? Would stiffening the damping help?

But wouldn't it still be better than having stiffer springs but crappy tyres?

Just for reference, my setup is koni shocks with RCE yellow springs 4.5kg square.

Sent from my LG-H815 using Tapatalk

Basically with sticky tires, your car grips hard enough and generates more cornering force so your car rolls more. In some cases it rolls onto the bumpstops if the springs are soft enough.

Yes, it will still be faster than stiff springs and crappy tires. Maybe not as fun, but faster.

Damping doesn't limit body roll in a steady state long corner, so it won't keep the car off the bumpstops in that case. It's felt in transitions, bumps, and corner entry/exit.

- Andrew

[strat61caster]

Originally Posted by Kayshart

For track situations, what would happen with a sticky tyre like AD08R with springs which are not stiff enough? Would this mean the suspension will be hitting the bumpstops through the corners? Would this worsen the car's handling? Would stiffening the damping help?

But wouldn't it still be better than having stiffer springs but crappy tyres?

Just for reference, my setup is koni shocks with RCE yellow springs 4.5kg square.

Sent from my LG-H815 using Tapatalk

If the car isn't tuned to utilize the bump stops it will probably create erratic behavior if the body roll is high enough and the bump stops are stiff enough. Basically the car will all of a sudden get an extremely high spring rate once the suspension gets compressed into the bump stops, any changes in the road surface like a bump or kerb when the car is riding on the bump stops will jolt the chassis likely causing a loss of grip, even potentially a very small one. Whether or not this would be the case with the soft-ish Ohlins or B16's (which are nearly double the spring rate of OE) and AD08's I can't say, but bump stops can be shortened.

On a smooth course with well chosen bump stops maybe nothing will happen, totally unnoticeable, I've heard that the new ND miata is rather bump stop active from the factory. But bump stops can create some very undesirable behavior, namely sudden at the limit under or oversteer.

Again, I don't know if the AD08's are sticky enough to cause this behavior, they are geared for street/track use and a somewhat reasonable life expectancy means they aren't total gumballs, it will also depend on the track and setup (raising the car up will allow for more travel and more predictable suspension behavior). When you start getting into this level of detail even people with similar setups may not be comparable as they run big fast courses where they load up the car a ton vs. quick short courses that won't generate the g's to overwork the suspension with that level of grip.

Agreed with racecomp, damping would only help reduce roll in the scenario where your cornering isn't sustained, like an autocross and that would be a crutch where you're removing ultimate grip in order to band-aid another problem (springs not being stiff enough, ride height too low, bump stops too tall/stiff).

[Tor]

Thanks a lot for your replies all of you!

The new Ohlins are very soft and I don't know if they have enough travel. We liked the old version on our car with the 6k and then custom 7k rates, but even then we wanted more stroke.

@Racecomp Engineering, I asked Öhlins Nürburgring center about the reason for the 4/3 spring rates. Their product manager is supposed to get back to me after xmas.

Another forum user in the German GT86 forum apparently got a reply that Öhlins Sweden found the 6/6 "to be too unstabile on the limit". If that translates into that they want to make the car understeer more in long fast curves, then fair enough and it might suit some.
Only it would be hard to justify the price in that case, as a driver looking for such setup would probably be equally satisfied with more reasonably priced dampers like KV V1, or ST XTA (1 way with top mounts for 1000 usd, I don't think you got that variant in the US?).

@strat61caster, I don't know if I would want to experiment with custom Bilsteins, as I don't think I am knowledgeable enough to undertake such task.
And their stock springs seems so different from anything else that is offered, that I don't know how to relate to it.

Can someone perhaps expand on the benefits/disadvantages of the exponential rates? And which rate (low/high) applies in which situation? Am I correct in assuming that the higher rates apply when the spring is compressed? And couldn't it make for some unpredictable dynamics if the spring are unequally loaded?


From what I can summarise, I guess the AD08R would require 6-8ish k springs?

No matter what I look at for options, it seem to circle back to KW Clubsport.

I still keep AST as an option. I sent an email to them to inquire about what spring rates they use for their AST 4100, and what they recommend for the AST 5100 (which allows customisation).
The 5100 is upside down. Say that two dampers are equal quality, is there a huge benefit to an upside down damper? They are 2000 and 2500 usd here respectively. With the relative small difference in the price, should I go for the 5100?

I'll also await the reply from Öhlins before making any decisions. Since no one seems to run those dampers + if they have a good explanation for the change + they give me an Godfatherlike offer like installation, alignment and track time at Nürburgring = I might go ahead and try them.

Thanks again everyone!

[strat61caster]

Originally Posted by Tor

@strat61caster, I don't know if I would want to experiment with custom Bilsteins, as I don't think I am knowledgeable enough to undertake such task.
And their stock springs seems so different from anything else that is offered, that I don't know how to relate to it.

Can someone perhaps expand on the benefits/disadvantages of the exponential rates? And which rate (low/high) applies in which situation? Am I correct in assuming that the higher rates apply when the spring is compressed? And couldn't it make for some unpredictable dynamics if the spring are unequally loaded?

The Bilstein spring rates are similar to OEM and most street oriented lowering spring options including Eibach which is supposedly the same as the TRD package with the rear being ~50% stiffer than the fronts. This also lines up with a few other setups like Tein SRC from CSG.

http://www.ft86club.com/forums/showthread.php?t=8739

They're different from the aftermarket that seems to like equal spring rates front/rear. Considering that the motion ratios in the rear mean that the effective spring rates in the rear are softer than the fronts given equal rates. Essentially the equal rates F/R results in a stiffer front than rear.

Here's an old thread from racecomp about it:
http://www.ft86club.com/forums/showthread.php?t=9936

I think you're correct, progressive spring rates aren't ideal and create a small question mark when it comes to how the car will react at the limit. Yes soft at initial compression and increasing spring rate upon increasing compression, but that's how most street cars are sprung, I believe the 86's stock springs are slightly progressive. It means a compliant ride on the public roads but stiffer springs when the car is pushed hard, reducing body roll when it's needed, but without creating harshness.

It's easy to say "yes, I'm all about maximum performance" and order what you think is best, but to live with that every day is an unknown until you do it.

Best of luck, there is no answer, only what makes you happiest.